Hitherto, an organic solvent has been used as a developer for photopolymerizable compositions but organic solvents generally are expensive, have toxic properties, and are combustible. Furthermore, due to the use of such an organic solvent, large costs are incurred for labor health and environmental pollution planning. Accordingly, a photopolymerizable composition which can be developed without using such an organic solvent has long been desired. In general, the component for determining the solubility and other properties of a photopolymerizable composition is a binder composition of the photopolymerizable composition.
Thus, photopolymerizable compositions capable of being developed by an alkaline aqueous solution are proposed, for example, in Japanese Patent Publication No. 14065/60 (wherein the binder is a polymer containing an oxyacid at the side chain), Japanese Patent Publication No. 32714/71 (corresponding to British Pat. No. 1,148,362) (wherein the binder is, for example, a methyl methacrylate/methacrylic acid copolymer), Japanese Patent Publication No. 34327/79 (corresponding to U.S. Pat. No. 3,804,631) (wherein the binder is, for example, a methyl methacrylate/2-ethylhexyl methacrylate/methacrylic acid terpolymer), Japanese Patent Publication No. 38961/80 (corresponding to U.S. (B1) Pat. No. 3,887,450) (wherein the binder is, for example, a styrene/maleic acid mono-n-butyl ester copolymer), Japanese Patent Publication No. 33413/81 (corresponding to U.S. Pat. No. 3,833,384) (wherein the binder is, for example, an ethyl methacrylate/ethyl acrylate/methacrylic acid terpolymer), Japanese Patent Publication No. 25957/79 (wherein the binder is, for example, a styrene/methyl methacrylate/ethyl acrylate/methacrylic acid quaternay copolymer), Japanese Patent Application (OPI) No. 99810/77 (wherein the binder is, for example, a benzyl methacrylate/methacrylic acid copolymer) (the term "OPI" indicates an unexamined published patent application open to public inspection), Japanese Patent Publication No. 12577/83 (wherein the binder is, for example, an acrylonitrile/2-ethylhexyl methacrylate/methacrylic acid terpolymer), and Japanese Patent Publication No. 6210/80 (corresponding to U.S. Pat. No. 4,353,978 ) (wherein the binder is, for example, a methyl methacrylate/ethyl acrylate/acrylic acid terpolymer and a styrene partially esterified by isopropanol/maleic anhydride copolymer).
However, the compositions described in these references described above may have some advantages but show certain disadvantages in the case of use as, in particular, a photoresist. A so-called dry film resist method including a step of laminating a solid photosensitive film on a substrate under pressure at the case of making a printed wiring plate using a substrate laminated with a metal foil such as, usually a copper foil is described in Japanese Patent Publication No. 25231/70 (corresponding to U.S. Pat. No. 3,469,982). The photopolymerizable composition suitable for the method is required to have a proper balance in, for example, developability, strippability (the resistance to an etching solution or plating solution in the polymerized state), low stickiness, high adhesive property for the substrate, and flexibility.
On the other hand, conventional photopolymerizable compositions which can be developed by an alkaline aqueous solution have one or more faults in that they are too sticky or brittle, they have insufficient adhesive property to substrate and insufficient swelling resistance for providing images having a high resolving power, and/or they need an excessively long developing time although they can be developed by an alkaline aqueous solution.
Also, recently, it has been desired to increase the density of printed circuits, and for that purpose, a dry film resist capable of providing a resist image which is faithful to an original and has a high resolving power is required.
However, conventional photopolymerizable compositions which can be developed by an alkaline aqueous solution are insufficient for this purpose. This is mainly based on that the photoresist layers are lacking in swelling resistance to a developer and in adhesion to the substrate.